1. Field of the Invention
The present invention relates to a method and apparatus for detecting trouble in either of pair of pulse generators.
2. Description of the Prior Art
In an internal combustion engine, when for example, the quantity and or timing of fuel injection by an injection pump is electronically controlled to obtain optimum engine operating conditions, it is essential for the control system to be provided with a reference pulse generator for generating a reference pulse each time the angular position of the rotating shaft of the fuel injection pump or the engine reaches a predetermined reference angular position, such as a position corresponding to the top dead center of a piston, and a cam-pulse generator for generating a cam pulse each time the shaft rotates by a predetermined angle. In such a system, the required fuel control operation is performed taking into account the time of the occurrence of the pulses. Accordingly, appropriate control operation cannot be assured when these pulse generators do not produce the respective pulses appropriately. Thus, there have been proposed various apparatuses for detecting trouble in pulse generators of this kind.
In U.S. Pat No. 4,395,905, for example, there is proposed a trouble detecting apparatus suitable for use with this kind of pulse generator. When pulses are not produced continuously by one or the other of the generators, the disclosed apparatus detects this trouble using the pulses produced by the other pulse generator. This prior art apparatus is effective for detecting that the pulses are not produced continuously but it is very difficult for it to detect trouble caused by a missing pulser cog of the pulse generator because this kind of trouble does not show up as a series of missing pulsees. The output when the pulser is missing a cog is similar to one including pulse noise, and the prior art apparatus is incapable of distinguising between these two types of trouble.